Proximity fuze



Jan. 7, 1964 H. E, TATEL ETAL PROXIMITY FUZE 2 Sheets-Sheet 1 Filed Nov.1, 1944 ATTORNEY Jan. 7, 1964 H. E. TATEL ETAL PROXIMITY FUZE 2Sheets-Sheet 2 Filed Nov. 1, 1944 ATTORNEY 3,l ideal Patented Jan. 7,1964 3,116,691 PRGHTY FUZE Howard E. Tatel and Lester S. Skaggs,Washington, D.C.,

assignors to the United States of America as represented by theSecretary of the Navy Filed Nov. 1, 1944, Ser. No. 561,438 12 Claims.(Cl. 1tl27tl.2)

This invention relates generally to electrically detonated projectilesand more particularly to an improved radio proximity fuze.

Radio proximity fuzes as customarily constructed up to the present timemake use of an antenna mounted at the forward end, or nose, of theprojectile. This type of antenna has been generally satisfactory inoperation, but is subject to the objectionable limitation that it isonly usable at relatively low frequencies (i.e. frequencies below 200me. for a projectile). At these lower frequencies, such an antenna willradiate a wave pattern, portions of the lobes of which extend slightlyforwardly with respect to the projectile, with the result that the fuzewill be triggered a fraction of a second before the projectile reachesthe target area. This is desirable for the reason that the fragmentationpattern of the projectile is such that shell fragments will be projectedslightly forwardly.

In order to render the fuze as versatile as possible with regard to theuse of frequencies, so that the possibility of jamming by an enemy, andthe eifect of water waves, will be reduced to a minimum, it has beenproposed to produce a fuze which will operate at frequencies much higherthan those now in use. When such higher frequencies, which are of theorder of 250 me. upward, are utilized in radio proximity fuzes with noseantennae of known varieties, however, it is found that the wave patternof the projectile is unsatisfactory. That is to say, the principal partof the radiation lobe is directed rearwardly rather than forwardly. Inorder to correct this unsatisfactory condition, it has been determinedthat the antenna should be mounted at the rear of the projectile,preferably projecting rearwardly. .Two broad classes of rear-antennaprojectiles may be considered. One of these entails the placement of allcircuit elements, detonators, and other parts, in a can in the base ofthe projectile, with an antenna adapted to project rearwardly. Thesecond class consists of an arrangement wherein the amplifier and othercomponents are placed in the nose of the projectile and electricallyconnected with an oscillator and antenna mounted at the base end of saidprojectile. Inasmuch as all of these components have already beendeveloped in a form suitable for nose mounting, particular considerationis herein given to the second mentioned class, the antenna andoscillator being placed in a can or container in the base of theprojectile because of the losses in RF. transmission lines. it will berecognized, however, that certain principles of this invention areequally applicable to both of the classes above defined.

One of the principal objects of the invention, therefore, is to providea radio proximity fuze wherein at least the oscillator and antenna aremounted in the base of the projectile, in such manner that asatisfactory wave pattern may be emitted at high frequencies.

Another object of the invention is to provide a radio proximity fuzewhich by reason of a favorable radiation pattern (roughly coincidentwith the fragmentation pattern of the projectile) will produce aprojectile of greater lethal effect than projectiles of this generalclass which have been developed up to the present time.

Another object of the invention is to provide an electrically detonatedprojectile of this character which may be readily adapted for use atvarious frequencies.

A further object of the invention is to provide such a radio proximityfuze which is compact and relatively simpie in construction and whichmay accordingly be conveniently mounted in the base of the projectile.

Still another object of the invention is to provide a fuze of thischaracter wherein the antenna is so arranged as to be held in aretnacted position within the projectile at all times prior to firing,but which will be released and projected to operative position by theforce of setback in conjunction with spring action, and/ or by someother suitable means, upon tiring.

Another object of the invention is to provide a radio proximity fuze ofthe indicatedchar-acter embodying a simple and highy eflicient grid andplate coil arrangement.

Other objects of the invention, not specifically mentioned hereinabove,will become apparent as the description proceeds.

In the drawings:

FIG. 1 is a longitudinal sectional view of a fuze constructed inaccordance with the present invention, showing the same with the antennain retracted position, and as the assembly appears installed in aprojectile, adjacent portions of which are also illustrated;

FIG. 2 is a rear elevational view of the projectile with fuze installed;

FIG. 3 is a view similar to but less complete than FIG. 1, showing theantenna extended and the closure plate and its retaining means detached;

-FIG. 4 is a schematic wiring diagram;

FIG. 5 is a diametric sectional view on a larger scale of the retainingnut for the base closure plate;

FIG. 6 is a plan view of the nut sectionally illustrated in FIG. 5; and

FIG. 7 is a perspective view of the coil supporting block which forms apart of the oscillator assembly.

The numeral 1 indicates generally the housing or can of our improvedfuze. The can 1 includes a tubular body 2 which is formed of steel orother suitable material and is reduced and counte-rbored at its forwardor inner end to form internal and external shoulders 4, 5. Near its rearend, the outer surface of the can is provided with a threaded course 6by which it is adapted to be supported in the base of a projectile as 3,a relatively thick radial flange 7 being formed at the rear end of thecan to seat in a suitable counterbored portion of the base, as shown.The can 1 is hollow throughout its length and is formed at its outer endwith a generally frusto-conical countersunk recess 8, which defines ashoulder 9. As best seen in FIGURE. 3 the recess 8 is provided with anannularly disposed series of generally semi-circular notches 10.

Closing the inner end of the can 1 is a peripherally flanged sleeve 13,the inwardly projecting central portion of which is hollow as indicatedat 16 to house the oscillator vacuum tube 18, while such central portionalso cooperates in supporting the antenna housing tube 34, threadedlyattached thereto at 14. The front flange 11 is mounted in thecounterbored front extremity 4 of the can.

The vacuum tube 18 is preferably of the rugged type disclosed in thecopending application of H. H. Porter et al., Serial 1N0. 519,518, filedJanuary 24, 1944; a rubber cushioning sock 17 being interposed betweenthe tube and sleeve and extending over the rear end of the tube toeffectively cushion it against setback.

Fitted about the sleeve portion '13 and abutting the flange 11 is a coilsupporting block 19 for-med of polystyrene or other suitable insulatingmaterial and seen in perspective in FIGURE 7. It will be observed thatsaid block is formed with a hub 20 and oppositely presenteddiametrically opposed wings 21 and 22. The wings 21 and 22 are aperturedto receive, respectively, the grid and plate coils of the oscillator,which coils are shown at 23 and 24 in FIGURE 1. Terminal portions of thecoils are projected through insulating bushings 25 and 26 which arecarried in openings 27 and 28 in the flange 11. The remaining componentsof the oscillator are contained in a polystyrene block 29 which abutsthe forward face of the flange 11. An end wall 3% closes the outer endof and [retains the block 29, these parts being held in place by asleeve 31 fitted there-about and mounted on the shouldered reducedportion of the can. The terminals of the grid and plate coils are heldunder tension by washers as 32 soldered to their corresponding outerends, an insulating disc 33 of semi-resilient material being retainedand somewhat compressed beneath each washer 32 to stress and rigidlyposition the parts.

The antenna housing sleeve 34 is screwed onto the threaded portion 14 ofthe sleeve 11 and extends axially throughout the major portion of thecan 1. The sleeve 34 is externally threaded at its rear end forreception of the coupling sleeve 36 which forms an extension thereof.The bore of the coupling sleeve tapers to decreased diameter toward itsrear end, the outer surface of the sleeve being reduced near its rearend and formed with buttress threads 38, for a purpose which willpresently appear.

The antenna rod 39 is normally contained within the sleeve 34, althoughduring operation it is projected rearwardly as shown in FIG. 3. Aslightly enlarged generally frusto-conic rear end portion 49 limitsextension of the antenna by coming up against the tapered bore of sleeve36 when the rod 39 is fully projected. Compression spring 43, trapped inthe sleeve 34, serves to project the antenna, which is normally held inthe retracted position, with the spring under compression, by a closureplate 44. Vents 44a in sleeve 134 permit entry of air as the antennaelement is projected to operative position.

Closure plate 44 is tapered from its mid-point toward its inner end toprovide a frusto-conic wall portion 45 adapted to seat in theconformably tapered recess 8 of the can 1 while allowing the closureplate to be forced out of the recess without possibility of jamming dueto cocking of the plate. Its fiat outer surface is provided with spanneropenings 46, to permit easy installation of the plate. concentricallyformed on the inner wall of therplate 44 is a boss 47, tapped to definea socket 43-. A copper gasket 51 is arranged under the plate to seal therear opening of the can.

The can 1 is also internally theraded at 52 near its rear end to supportthe guide sleeve 53, of polystyrene or other suitable insulatingmaterial. The guide sleeve supports and positions the antenna tube andcoupling sleeve assembly. The end cover plate 44 is held to the couplingsleeve 36 by a displaceable split nut 54 which includes a threaded baseor ring portion 55 screwed into the socket 48, the remainder of the nutbeing constituted of a plurality of segments 56 arranged as shown inFIGURES 5 and 6. Each segment includes a relatively massive radiallyprojecting section and a threaded inner surface coacting with thebuttress threads 38 on the coupling sleeve 35. The buttress threads arecapable of supporting large tensile loads without translating anyappreciable fraction of such loads into radial thrust, which would tendto cause the split nut to expand and become disengaged from the couplingsleeve 36. Each segment '56 is connected to the base or ring portion 55by a web 5'7.

When the projectile is fired, the force of set back causes the nut 54 tospread, bending the segments 56 on their web-s 57 as shown in FIG. 3,due to the fiact that said segments overhang the web to -a considerabledegree. The plate and nut assembly are thus freed. After the projectilehas emerged from the gun, the spring displaces the plate and nutassembly from the recess 8, and projects the antenna to operativeposition as shown in FIG. 3.

Referring more particularly to the oscillator circuit, shown in "FIGURE4, it will be noted that the antenna element 39 is grounded to the canand projectile through the housing 34. Vaccum tube 13 includes a grid53, a filamentor cathode 5? and a plate or anode 6d. The grid coil orinductance 2.3 has one terminal connected to the grid and the othergrounded to the can 1. The plate coil 24 has one terminal connected tothe plate 6% and the other connected to the junction of a bypasscondenser 61 and a radio frequency choke 62. The opposite terminal ofthe choke is connected to the positive l3 battery terminal. The negativeB battery terminal and the negative A battery terminal are alsogrounded. The positive A battery terminal is connected to the filament59 by a suitable condoctor.

It will be understood that this circuit arrangement may be varied asdesired, and that, when installed, the output terminals of theoscillator are connected to suitable amplifier and firing means (formingno part of our present invention and accordingly not shown) which may,as previously indicated, be mounted in the nose or other portion of theprojectile.

The electrical circuits, when rendered effective by suitable armingmeans (not shown) are adapted to fire the projectile when it approachesa target. The operation and arrangement of the other electrical circuitsand components are preferably similar to those of the radio proximityfuze forming the subject matter of copending application of M. A. Tuveet 'al., Serial No. 471,388, filed January 6, 1943.

Our invention provides a radio proximity fuze which is adapted tooperate on a Wide range of frequencies. As a result, the possibility ofjamming is reduced to a minimum. The mechanism is nevertheless of simpleconstruction and capable of withstanding the stresses present in aprojectile during acceleration.

The can 1 defines a cavity which permits the oscillator to be coupled tothe antenna most efticiently. The cavity also reduces losses with theresult that the oscillator has higher Q (ratio of stored energy todissipated energy). As will be observed, one side of the filament isconnected to the ground, thus eliminating the need for chokes in thefilament circuit and, accordingly, reducing losses due to their use. Inview of the fact that separate plate and grid coils, inductivelycoupled, are employed, the circuit components may be connected at pointsof low RF. voltage.

We claim:

1. In a radio proximity fuze for projectiles, means for generatingelectromagnetic waves including a can defining an oscillator cavity, andan antenna mounted within the can and movable to a position extendingtherefrom when the projectile is fired, s aid oscillator and saidantenna being electrically connected so that said antenna emits saidelectromagnetic Waves for reflection by a target.

2. A radio proximity fuze for projectiles including a can adapted to bemounted in the base of a. projectile, an oscillator mounted in the canat one end thereof, an antenna mounted within the can and electricallyconnected with the oscillator, means for urging the antenna toward anoperative position extending from the can, and means for normallyretaining the antenna in an inoperative position within the can andagainst the compression of said last mentioned means, said retainingmeans being releasable by the force of set back upon firing of theprojectile for releasing the antenna whereby said antenna will beprojected to operative position for emitting radiation generated by theoscillator.

3. A radio proximity fuze including a can to be mounted in a projectile,an oscillator mounted within the can, an antenna element housing sleevemounted spacedly within and substantially coaxial with respect to thecan and an antenna element in the housing sleeve, said antenna elementbeing movable from an inoperative position in the sleeve to an operativeposition extending from said sleeve for emitting radiation generated bythe oscillator.

4. A radio proximity fuze including a substantially tubular can, anoscillator supporting sleeve spacedly mounted Within and substantiallyaxially of the can, a coil supporting block carried by the sleeve,oscillator means including a vacuum tube carried within the sleeve, gridand plate coils carried by the block, means carried by the oscillatorsupporting sleeve for mounting other oscillator components, said can dolning an oscillator cavity, and an antenna normally carried Within thecan and movable to an operative position extending from the can forradiating energy generated by the oscillator.

5. A radio pr iuze including a can, a socketed oscillator mountingsleeve therein, an antenna housing sleeve connectc extending lcngi 11yterminating near one end of the can, a 00 g sleeve connected with andforming a continuation of the hot-sing sleeve at said end of the can andhaving a tapered internal Wall forming a reduced portion at said end, anantenna element slidably mounted in the housing sleeve and couplingsleeve and having a generally trusts-conical portion near one endadapted to coact with said reduced portion, and a spring confined withinthe housing sleeve between the socket and the inner end of .e antennaelement, said an tenna element being movable by said spring from aninoperative position Within the housing sleeve to operative positionextending from said sleeve, the frusto-conical portion being engagevabieWith the reduced portion of the coupling sleeve to limit outwardmovement of the antenna element and assure positive electricalconnection between the ho g sleeve and said antenna. element.

6. In a radio proximity fuze as recited in claim 5, means normallyretaining the antenna element Within the housing sleeve and against thecompression of the s ring.

7. In a radio proximity fuze as recited in claim 5, means for normallyretaining the antenna element Within the housing sleeve and against thecompression of the spring, said means including a retaining closureportion mounted in the outer end of the can, and a split nut operativelyconnecting the closure plate with the coupling sleeve, said split nuthaving hcldin pontions displaceable by setback upon firing of theprojectile for releasing the closure plate from the coupling sleeve.

8. in a fuzed projectile assembly, a can mounted in the projectile,means Within the can for generating nadio frequency energy, antennacarried by the can and projectable therefrom, said antenna beingopenatively connected With said means When in the projected position,means nomally retaining said antenna Within said can, and meansresponsive to forces resulting from firing said projectile for freeingand projecting said antenna.

9. In a fuzed projectile assembly, a cylindrical can coaxially mountedwithin the projectile, means for generating electro-rnagnetic Waves, anantenna element axially mounted in said can and movable from aninoperative position within said can to an operative position extendingtherefrom.

10. An arrangement as set forth in claim 9, in which said generatingmeans comprises an oscillator arranged in and near one end of said can.

1 l. A radio proximity fuze including a canto be mountin a projectile,an oscillator mounted Within the can, an antenna element housing sleevemounted spacedly Within and substantially coaxial with respect to thecan and an antenna element in the housing sleeve, means for normallyretaining the antenna Within the housing sleeve in an inoperativeposition, including a retaining element, a releasable com: cting eleme ttying said retaining element to said sleeve, said connecting elementincluding a portion releasable by the force of setback to free saidretaining means, whereby said antenna element may move from saidinoperative position to an operative position of the antenna elementprojecting from said can.

12. A radio proximity fuze including a canto be mounted in a projectile,an oscillator mounted Within the can, an antenna element housing sleevemounted spacedly within and substantially coaxial with respect to thecan and an antenna element in the housing sleeve, means for normallystaining the antenna Within the housing sleeve in an in ope aliveposition, including a renal ing element, a releasable connecting elementtying said retaining element to said sleeve, said connecting elementincluding portions shifts 1e by the force of set back to release saidretaining means whereby said antenna element may move from saidinopenative position to an operative position of the antenna elementprojecting from said can, said connecting element further including asplit nut having a base portion, a plurality of segments, and a web forconnecting each of said segments with said base portion.

References Cited in the file of this patent UNITED STATES PATENTS

9. IN A FUZED PROJECTILE ASSEMBLY, A CYLINDRICAL CAN COAXIALLY MOUNTEDWITHIN THE PROJECTILE, MEANS FOR GENERATING ELECTRO-MAGNETIC WAVES, ANANTENNA ELEMENT AXIALLY MOUNTED IN SAID CAN AND MOVABLE FROM ANINOPERATIVE POSITION WITHIN SAID CAN TO AN OPERATIVE POSITION EXTENDINGTHEREFROM.